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Neuromyelitis Optica Spectrum Disorder (NMOSD)

(Neuromyelitis Optica; Devic Disease)


Michael C. Levin

, MD, College of Medicine, University of Saskatchewan

Full review/revision Mar 2021 | Modified Sep 2022
Topic Resources

Neuromyelitis optica spectrum disorder affects mainly the nerves in the eyes and spinal cord, causing patches of myelin (the substance that covers most nerve fibers) and the nerve fibers under them to be damaged or destroyed.

Nerve Cells and Fibers

The risk of becoming disabled is greater with neuromyelitis optica spectrum disorder than with multiple sclerosis. Thus, people with symptoms suggesting neuromyelitis optica spectrum disorder should see a doctor promptly.

Insulating a Nerve Fiber

Most nerve fibers inside and outside the brain are wrapped with many layers of tissue composed of a fat (lipoprotein) called myelin. These layers form the myelin sheath. Much like the insulation around an electrical wire, the myelin sheath enables nerve signals (electrical impulses) to be conducted along the nerve fiber with speed and accuracy. When the myelin sheath is damaged (called demyelination), nerves do not conduct electrical impulses normally.

Insulating a Nerve Fiber

Neuromyelitis optica spectrum disorder is also an autoimmune disorder Autoimmune Disorders An autoimmune disorder is a malfunction of the body's immune system that causes the body to attack its own tissues. What triggers an autoimmune disorder is not known. Symptoms vary depending... read more . Autoimmune disorders occur when the immune system malfunctions and attacks the body’s own tissues. In neuromyelitis optica spectrum disorder, the target of the autoimmune attack is a protein called aquaporin 4, which is present on the surface of support cells (called astrocytes) in the brain, spinal cord, and optic nerves. Damage to astrocytes is thought to lead to demyelination. In some people with neuromyelitis optica spectrum disorder, the immune system targets another protein called myelin oligodendrocyte glycoprotein (MOG), which is present on the outer layer of myelin.

Symptoms of NMOSD

Neuromyelitis optica spectrum disorder causes inflammation of the optic nerve (optic neuritis Optic Neuritis Optic neuritis is inflammation of the optic nerve. Multiple sclerosis is the most common cause. Loss of vision may develop, and there may be pain with eye movement. Magnetic resonance imaging... read more ). One or both eyes may be affected. The disorder causes episodes of eye pain and dim, blurred, or lost vision.

Some people have hiccups that will not stop (persistent or intractable hiccups Causes ) or nausea and vomiting.

In some people, the part of the spinal cord that controls breathing is inflamed, leading to difficulty breathing, which is life threatening.

Neuromyelitis optica spectrum disorder progresses differently in each person. As the disorder progresses, people may have brief, frequent, painful muscle spasms. Eventually, blindness, loss of sensation and muscle weakness in the limbs, and bladder and bowel dysfunction may become permanent.

Diagnosis of NMOSD

  • A doctor's evaluation

  • Magnetic resonance imaging

  • Evoked responses

  • Blood tests

Usually, tests include magnetic resonance imaging (MRI) of the brain to rule out multiple sclerosis. MRI of the spinal cord and evoked responses Evoked Responses Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more Evoked Responses are done to help confirm the diagnosis of neuromyelitis optica spectrum disorder.

When the evoked responses test is used to diagnose neuromyelitis optica spectrum disorder, stimuli for sight (such as a flashing light) are used to activate certain areas of the brain. Then, electroencephalography Electroencephalography Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Electroencephalography (EEG) is a simple, painless procedure in which... read more Electroencephalography is used to detect the response to the stimuli. Based on these responses, doctors can tell how well the optic nerve is working.

Blood tests to detect specific antibodies to aquaporin 4 and to myelin oligodendrocyte glycoprotein may be done to distinguish neuromyelitis optica spectrum disorder from multiple sclerosis. (Antibodies Antibodies One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more Antibodies are proteins produced by the immune system to help defend the body against a particular attacker.)

Treatment of NMOSD

  • Corticosteroids

  • Plasma exchange

  • Drugs that suppress the immune system

There is no cure for neuromyelitis optica spectrum disorder. However, treatments can stop episodes, control symptoms, and prevent episodes from recurring.

A corticosteroid (such as methylprednisolone) and a drug that suppresses the immune system (an immunosuppressant, such as azathioprine) are often used to stop and prevent episodes.

Satralizumab and inebilizumab (both monoclonal antibodies) can be used to treat neuromyelitis optica spectrum disorder when aquaporin-4 antibodies are present. People taking these drugs are closely monitored for infections, such as urinary tract and respiratory infections.

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